Download State-Space Representation for Digital Waveguide Networks of Lossy Flared Acoustic Pipes This paper deals with digital waveguide modeling of wind instruments. It presents the application of state-space representations to the acoustic model of Webster-Lokshin. This acoustic model describes the propagation of longitudinal waves in axisymmetric acoustic pipes with a varying cross-section, visco-thermal losses at the walls, and without assuming planar or spherical waves. Moreover, three types of discontinuities of the shape can be taken into account (radius, slope and curvature), which can lead to a good fit of the original shape of pipe. The purpose of this work is to build low-cost digital simulations in the time domain, based on the Webster-Lokshin model. First, decomposing a resonator into independent elementary parts and isolating delay operators lead to a network of input/output systems and delays, of KellyLochbaum network type. Second, for a systematic assembling of elements, their state-space representations are derived in discrete time. Then, standard tools of automatic control are used to reduce the complexity of digital simulations in time domain. In order to validate the method, simulations are presented and compared with measurements.
Download Power-balanced Modelling Of Circuits As Skew Gradient Systems This article is concerned with the power-balanced simulation of analog audio circuits, governed by nonlinear differential algebraic equations (DAE). The proposed approach is to combine principles from the port-Hamiltonian and Brayton-Moser formalisms to yield a skew-symmetric gradient system. The practical interest is to provide a solver, using an average discrete gradient, that handles differential and algebraic relations in a unified way, and avoids having to pre-solve the algebraic part. This leads to a structure-preserving method that conserves the power balance and total energy. The proposed formulation is then applied on typical nonlinear audio circuits to study the effectiveness of the method.
Download Compositional Application of a Chaotic Dynamical System for the Synthesis of Sounds The paper presents a review of compositional application developed in the last years using a chaotic dynamical system in different
sound synthesis processes. The use of chaotic dynamical systems
in computer music has been a widespread practice for some time
now. The experimentation presented in this work shows the use
of a specific chaotic system: the Chua’s oscillator, within different
sound synthesis methods. A family of new musical instruments
has been developed exploiting the potential offered by the use of
this chaotic system to produce complex timbres and sounds. The
instruments have been used for the creation of musical pieces and
for the realization of live electronics performances.
Download Full mesh warping techniques This paper discusses methods for the elimination of dispersion in a digital waveguide mesh. As in previous methods, a highly isotropic waveguide mesh is chosen as a starting point, reducing the problem to compensation of frequency-dependent dispersion. For this purpose, as an alternative to Savioja and Välimäki’s technique of frequency-warping the input/output signals, we propose (1) inhomogeneous allpass-warping of delay elements, which enables use of allpass filters without introducing delay-free loops, and (2) “mass loading” the mesh in such a way that high-frequency propagation speed is increased to partially compensate dispersion due to quantization over a grid.
Download A Study on Dynamic Vocal Tract Shaping for Dipthong Simulation Using a 2D Digital Wavegude Mesh This paper presents a study of an articulatory-based speech synthesis based on a 2D-Digital Waveguide Mesh (2D-DWM) to model acoustic wave propagation in the oral tract. It is employed to study the effects of changing oral tract area, and in particular, of moving the articulators during the production of diphthongs. The operation of the synthesizer including details of how diphthongs are produced are discussed. The results support earlier findings that the wall reflection coefficient is inversely proportional to the formant bandwidth.
Download Sound Generation with Aperiodic Ordered Systems Aperiodic 1D systems introduced in physics in the field of quasicrystals are used in this work, in order to generate selfsimilar aperiodic time structures. The Fourier analysis of series of impulses distributed in time in a non periodic but ordered way, shows that for some cases the spectrum has a discrete part that can be used for sound synthesis.
Download Topologizing Sound Synthesis via Sheaves In recent years, a range of topological methods have emerged for
processing digital signals. In this paper we show how the construction of topological filters via sheaves can be used to topologize
existing sound synthesis methods. I illustrate this process on two
classes of synthesis approaches: (1) based on linear-time invariant digital filters and (2) based on oscillators defined on a circle.
We use the computationally-friendly approach to modeling topologies via a simplicial complex, and we attach our classical synthesis
methods to them via sheaves. In particular, we explore examples
of simplicial topologies that mimic sampled lines and loops. Over
these spaces we realize concrete examples of simple discrete harmonic oscillators (resonant filters), and simple comb filter based
algorithms (such as Karplus-Strong) as well as frequency modulation.
Download Measuring Diffusion in a 2D Digital Waveguide Mesh The digital waveguide mesh is a method by which the propagation of sound waves in an acoustic system can be simulated. An important consideration in modelling such systems is the accurate modelling of reflection characteristics at boundaries and surfaces. A significant property of an acoustic boundary is its diffusivity. In fact partially diffuse sound reflections are observed at most real acoustic surfaces and so this is an important consideration when implementing a digital waveguide mesh model. This paper presents a method for modelling diffusion that offers a high degree of control. The model is implemented with varying amounts of diffusivity, and a method for measuring its diffusive properties is outlined. Results for the model are presented and a method to calculate the diffusion coefficient is described.